Transmissions are used to transfer a drive torque from a drive unit to a load. For example, a vehicle transmission transfers the drive torque from the vehicle engine to the vehicle load. Some transmissions include a finite set of gears, which may be selected to produce a specific transmission ratio. Other transmissions may include a ratio varying unit (“variator”) to provide a substantially continuous variation of transmission ratio rather than a series of predetermined transmission ratios. Such transmissions are typically referred to as continuously variable transmissions (CVTs), infinitely variable transmissions (IVTs), toroidal transmissions, and/or the like.
Typical transmissions include one or more clutches. One type of clutch that may be used in a transmission, as well as other devices is known as a roller clutch. Conventional roller clutches can be used as one-way or overrunning clutches to allow freewheeling of an output (e.g., an output shaft) relative to an input (e.g., an input shaft) depending on the torque interaction of the input and output. For example, vehicle transmissions may include one-way clutches, such as a roller clutch, sensitive to torque differentials to connect an input shaft to an output shaft to allow freewheeling of a drive train between a drive unit and a vehicle load when direct connection of the drive unit to the vehicle load is undesirable. One example of such a conventional roller clutch is shown in FIGS. 6-7D. Similar devices such as sprag clutches and ratchets can also be used to provide one-way or overrunning clutch relationships between inputs and outputs.